1. Field of the Invention
The present invention relates to semiconductor laser devices and, more particularly, is directed to a semiconductor laser device in which a lead member having a mounting portion for a semiconductor laser and other lead members are unitarily molded by a resin mold.
2. Description of the Prior Art
Semiconductor laser devices have been employed in various fields such as a light source of a recording/reproducing apparatus for an optical disk, magneto-optical disk or the like.
The ordinary semiconductor laser device includes a semiconductor laser and a photo detecting element such as a photo diode for monitoring an illumination state of the semiconductor laser so as to control the semiconductor laser to thereby automatically control an output power thereof at a constant level. In the ordinary semiconductor laser device, both the semiconductor laser and photo detecting element are sealed in a can package.
In the can package sealing, for example, three leads are extracted from the semiconductor laser and the photo diode. Among the three leads, two leads respectively serve as two power supply terminals for the laser and diode, and remaining one lead serves as one common terminal for the laser and diode. Both the semiconductor laser and the photo diode are mounted on a header portion, and the header portion is covered by a can having a window sealed by a glass plate for passing a front light beam radiated from the laser. Both the header portion and the can are sealed with each other.
The thus constituted can package sealing has a disadvantage that assembling processes such as a positioning process for respective parts and a sealing process between the header and can are troublesome.
In contrast, there has been proposed such a semiconductor laser device as shown in FIG. 1 which has the following structural features.
Referring to FIG. 1 of the accompanying drawings, a semiconductor laser LD is mounted on a sub-mount substrate 1 made of silicon or the like together with a photo detecting element, for example, photo diode PD for receiving a laser beam radiated from the semiconductor laser so as to monitor the laser beam. The sub-mount substrate 1 is mounted, that is, die bonded on a lead 3 which penetrates through a resin substrate 2. Respective electrodes of the semiconductor laser LD and the photo diode PD are connected via lead wires 4 to other two leads 3 which also penetrate the resin substrate 2. A transparent resin mold 5 covers the lead wires, bonding portions thereof and bonding portions of both the semiconductor laser LD and the photo diode PD so as to seal them.
However, the thus constituted semiconductor laser device has disadvantages such that, in the sealing process of both the semiconductor laser LD and the photo diode PD by the resin mold 5, stress is applied to the laser and the photo diode due to shrink of the resin mold 5 or the like when it is hardened, thereby degrading the yield of the device. Further, the aberration may be caused in the laser beam generated by the semiconductor laser LD due to the flow of the resin in the sealing process and insufficient flatness of the resin surface or the like to thereby degrade the characteristic of the semiconductor laser device. Furthermore, since the resin used is required to be transparent, the material used for the resin mold is disadvantageously limited.